Resistive-switching memory elements having improved switching characteristics

Abstract

Resistive-switching memory elements having improved switching characteristics are described, including a memory element having a first electrode and a second electrode, a switching layer between the first electrode and the second electrode comprising hafnium oxide and having a first thickness, and a coupling layer between the switching layer and the second electrode, the coupling layer comprising a material including metal titanium and having a second thickness that is less than 25 percent of the first thickness.

1. A method for forming a resistive-switching memory element comprising:
 depositing a first electrode on a substrate; 
 depositing a first layer comprising a metal oxide on the first electrode; 
 depositing a second layer on the first layer, the second layer comprising titanium metal; 
 depositing a second electrode on the second layer; 
 forming titanium oxide in a portion of the second layer, wherein forming the titanium oxide creates oxygen vacancies in the first layer, the oxygen vacancies having uneven distribution throughout the first layer. 
 
     
     
       2. The method of  claim 1 , wherein the first layer comprises a metal oxide chosen from the group consisting of cerium oxide, hafnium oxide, aluminum oxide, tantalum oxide, yttrium oxide, and zirconium oxide. 
     
     
       3. The method of  claim 1 , wherein the first layer comprises a metal oxide chosen from the group consisting of p-type zinc oxide and p-type copper oxide. 
     
     
       4. The method of  claim 3 , further comprising
 doping the first layer to form a p-type metal oxide layer. 
 
     
     
       5. The method of  claim 1 , wherein depositing the first layer comprises at least one of atomic layer deposition (ALD) and plasma-enhanced ALD (PEALD). 
     
     
       6. The method of  claim 5 , wherein depositing the first layer comprises using one or more of water vapor, isopropyl alcohol (IPA), and ethanol. 
     
     
       7. The method of  claim 5 , wherein the ALD is performed at a temperature of the substrate of less than 250 degrees Celsius. 
     
     
       8. The method of  claim 1 , wherein the second layer has a thickness that is less than 25 percent of a thickness of the first layer. 
     
     
       9. The method of  claim 1 , wherein depositing the first layer comprises oxidizing a portion of the first electrode and forming the metal oxide of the first layer. 
     
     
       10. The method of  claim 9 , wherein oxidizing is controlled using a specific oxygen source and maintaining a specific vapor pressure of the oxygen source. 
     
     
       11. The method of  claim 10 , wherein maintaining the vapor pressure comprises one of controlling a temperature of the oxygen source and diluting the oxygen source with an inert gas. 
     
     
       12. The method of  claim 11 , wherein the oxygen source comprises water vapor and wherein the oxygen source is maintained at a temperature of between 0 degrees Celsius and 10 degrees Celsius. 
     
     
       13. The method of  claim 11 , wherein the oxygen source comprises one or more of isopropyl alcohol (IPA) and ethanol. 
     
     
       14. The method of  claim 1 , wherein forming titanium oxide comprises oxygen migration between the first layer and the second layer. 
     
     
       15. The method of  claim 1 , wherein the second layer is free of titanium oxide prior to forming titanium oxide. 
     
     
       16. The method of  claim 1 , wherein, after forming titanium oxide, a portion of the second layer interfacing the first layer is free of metallic titanium and a portion of the second layer interfacing the second electrode is free of titanium oxide. 
     
     
       17. The method of  claim 1 , wherein oxygen is gradually varied throughout the second layer. 
     
     
       18. The method of  claim 1 , wherein oxygen is gradually varied throughout the first layer.